1. Field of the Invention
The present invention relates to a display device. In particular, the present invention relates to a display device capable of displaying a three-dimensional (3D) image.
2. Description of the Related Art
Display devices are widely used, ranging from large display devices such as television devices to small display devices such as mobile phones. The display device includes a display portion in which a plurality of pixels are provided in matrix. An image is formed on the display portion in such a manner that each of the pixels displays a predetermined color. In recent years, display devices capable of displaying 3D images have been developed.
An example of a display method for displaying 3D images is a method (hereinafter also referred to as a stereoscopic method) which has a period in which display for a left eye is performed on a display portion and a period in which display for a right eye is performed on the display portion. In this method, a viewer wears glasses with which the display for the left eye is perceived only by the left eye and the display for the right eye is perceived only by the right eye. Another example of a display method for displaying 3D images is a method (hereinafter also referred to as an autostereoscopic method) which uses pixels for a left eye and pixels for a right eye in a display portion and utilizes a structure (a parallax barrier or the like) with which the display for the left eye is perceived only by the left eye and the display for the right eye is perceived only by the right eye.
It is not necessary to prepare glasses to see 3D images in the case of autostereoscopic display, which offers high convenience. Note that when two-dimensional (2D) images are displayed with a display device for autostereoscopic 3D display, the resolution of the 2D images is low because of a structure unique to an autostereoscopic method (a parallax barrier or the like).
Patent Document 1 discloses a display device in which the resolution of 2D images can be prevented from being decreased in the case of the display device for 3D images with the use of an autostereoscopic method. Specifically, the display device disclosed in Patent Document 1 forms a parallax barrier with the use of liquid crystal whose alignment state is controlled by a voltage applied thereto. With this structure, it is possible to determine whether or not a parallax barrier is used in the display device.
That is, the display device can display 3D images when the parallax barrier is used and can display 2D images when the parallax barrier is not used.